1. Field of the Invention
The present invention relates generally to seats for vehicles and, more specifically, to a power seat height adjuster mechanism for an automotive vehicle.
2. Description of the Related Art
It is known to provide a seat for a vehicle such as an automotive vehicle. Typically, the seat includes a generally horizontal seat portion and a generally vertical back portion operatively connected to the seat portion. The seat may include at least one, preferably a pair of tracks to allow horizontal adjustment of the seat portion and a pivoting mechanism to allow vertical adjustment of the seat portion. The height of the seat portion may be manually adjusted or by power.
There are an increasing number of electrically actuated components in an automotive vehicle, such as seat height adjusters, power window regulators, steering column adjusters, rear-view mirror wipers, window screen wipers, antennas regulators, sunroof adjusters, headlamps adjusters, oil pumps or water pumps. All of these components can be driven by electric motors; the size of the motor is directly linked to the couple it must provide to produce the required motion. Because of friction and backlash, it is difficult to control large output torques if they are obtained from an electric motor through a gear train. If no gearing is used, it is possible to accurately control torque output, but large torques are not possible unless heavy direct-drive motors and high-powered current amplifiers are used.
Specifically, the linear motion of a driven element, e.g. a screw, allows it to adjust the height position of an automotive seat in the presence of an input torque, regardless of the direction of rotation of the motor shaft. In addition, by a continuously operating mechanism, a position holding function of the mechanism has to be performed, regardless of the presence (crash accident) or absence (stationary height adjusted position) of the input torque.
These mechanisms are available to allow the input drive mechanism to operate the actuated element, e.g. automotive seat, in either of the two directions of rotation of the input drive. If the actuated element is permitted to be moved by the external forces (weight of the passenger or reaction forces in a crash accident), a loss in control of the actuated element may result, which is unacceptable. In addition, these external forces may backdrive the input drive mechanism, and such back forces may be detrimental to the drive motor.
The above-described seat height adjusters may subject the seat to a drop in height because rotation of the screw under the load due to vibrations, when the input torque is not present. Also, these seat height adjusters do not have reliable self-locking capability, making a total dynamic self-locking capability impossible. Further, these seat height adjusters have a low efficiency transmission.
Therefore, it is desirable to provide a power seat height adjuster mechanism for a seat of a vehicle that has an anti-backdrive spindle drive utilizing a self-locking power take-off transmission mechanism. It is also desirable to provide a power seat height adjuster mechanism for a seat of a vehicle that has an anti-backdrive spindle drive, which has a compact design in order to meet required limited space underneath a seat of an automotive vehicle. It is further desirable to provide a power seat height adjuster mechanism for a seat of a vehicle that has an anti-back drive spindle, which has a higher total efficiency of transmission. It is still further desirable to provide a power seat height adjuster mechanism that has an anti-backdrive spindle, which can be easily assembled and manufactured at a relatively low cost. Thus, there is a need in the art to provide a power seat height adjuster mechanism that meets at least one of these desires.